Hollow-weave airbag

ABSTRACT

A hollow-weave airbag is constituted of a bag portion ( 11 ) with a 1/1 bag structure, and a closed portion ( 12 ) that has two or more weave structures and adjoins the bag portion  11 . In addition, the closed portion ( 12 ) is constituted of, in sequence from the bag portion side, a first weave structure  12 A with a 2/2 structure, a second weave structure  12 B with a 1/1 structure, and a third weave structure with a 3/3 structure. Furthermore, the 2/2 structure is constituted of 3 to 5 weft yarns, and the 1/1 structure is constituted of 2 to 5 weft yarns.

FIELD OF THE INVENTION

This invention relates to a hollow-weave airbag. More specifically, itrelates to a hollow-weave airbag that suppresses opening of stitches ata boundary of a bag portion and a closed portion even on deployment and,as well as being able to secure sufficient airtightness, is able tomaintain a deployed state for a certain period of time or more.

BACKGROUND OF THE INVENTION

Hollow-weave airbags are used for purposes such as absorbing impacts bybeing caused to deploy through air being fed instantly into a bagportion structure and maintaining that deployed state for apredetermined period of time.

In recent years, these hollow-weave airbags have been used in variousapplications. For example, hollow weave airbags are used in lifejackets, life boats, mats, home elevators, and have been installed invehicles where, by deploying when a vehicular collision occurs, they areused as airbags that protect the head and chest portions of vehicleoccupants.

In addition, one of the most important requirements for this kind ofhollow-weave airbag is that a bag portion of the airbag should haveexcellent airtightness, such that it is able to deploy and maintain aninflated state. Furthermore, in recent years, many of the airbags thatare installed in vehicles have been provided at vehicle pillars and seatsides, in order to protect the side of the head of a vehicle operator inthe event of a roll-over or an impact from the side. It is necessarythat this type of airbag secures the deployed state for a certain periodof time in order to protect the head of a vehicle occupant, not only atthe point of impact but also during the roll-over or the likeafterwards. In recent years, therefore, it has been highly important forhollow-weave airbags to possess not only excellent airtightness, butalso be able to secure the deployed state for the certain period oftime, and be compactly storable to enable provision in the pillars orseat sides of the vehicle.

Depending on the structure, however, some hollow-weave airbags arelikely to cause stitches at a boundary of the bag portion and a closedportion to open on deployment of the airbag due to air pressure insidethe airbag. If this opening of stitches occurs on deployment,airtightness decreases, causing strength insufficiencies at the boundaryportion or gas leaks. As a result, it may become difficult to maintainthe airbag in the deployed state for a certain period of time or more.

Various airbags have been developed in order to solve this problem. Forexample, in Japanese Patent Laid-Open Publication No. 2000-229550, ahollow-weave airbag is disclosed that is formed with a triple weaveportion and a quadruple weave portion, which have a yarn density ratiolower than a circumferential edge portion, in a peripheral area thatincludes a boundary of the bag portion and the closed portion, and wherea coating layer is formed not only on a front face side, but also on aback face side by using a coating agent that permeates to the back side.Furthermore, in Japanese Patent Laid-Open Publication No. 2001-233153, ahollow-weave airbag is disclosed that has a 3/n basket weave structure(n is an integer of 2 or more) of only one warp yarn at the boundary ofthe bag portion and the closed portion on a single-layered structure.The single-layered structure other than the boundary of the bag portionand the closed portion has a 3/n basket weave structure (n is an integerof 2 or more) that has n warp yarns in a continuous fashion with theboundary portion, and a cover factor on the single-layered structure of4,000 or more.

Although the hollow-weave airbags disclosed in both Japanese PatentLaid-Open Publication No. 2000-229550 and Japanese Patent Laid-OpenPublication No. 2001-233153 possess airtightness superior toconventional hollow-weave airbags, however, it is necessary to carry outa separate coating process in order to form a coating layer in theformer hollow-weave airbag, which makes the manufacturing processcomplicated and is also likely to increase costs. Furthermore, if thecoating layer becomes too thick, folding up the airbag compactly maybecome difficult. On the other hand, although the latter hollow-weaveairbag has superior airtightness, densifying the weave structure at theboundary in order to prevent opening of stitches at the boundary of thebag portion and the closed portion expands the boundary and makes thecoating layer susceptible to non-uniformity, and as a result, compactfolding may become difficult. Furthermore, although it is preferablethat the weave structure of the boundary of the hollow-weave airbag beof a curved-line structure rather than a straight-line structure, inorder to increase freedom of design as well as so that gas pressure issuitably dispersed rather than stress being concentrated, no mention ismade in the above laid-open publications of how to maintain airtightnessin the event that the weave structure at the boundaries is given thecurved-line structure.

SUMMARY OF THE INVENTION

The invention is contrived in view of the foregoing problems, and it isan object of the invention to provide a hollow-weave airbag thatsuppresses opening of stitches at a boundary of a bag portion and aclosed portion even on deployment and, as well as being able to securesufficient airtightness, is able to maintain a deployed state for acertain period of time or more.

A hollow-weave airbag according to a first aspect of the invention isconstituted of a bag portion and a closed portion that has two or moreweave structures and adjoins the bag portion. The closed portion isconstituted of, in sequence from the bag portion side, a first weavestructure and a second weave structure, which adjoins a side of thefirst weave structure opposite the bag portion side, and the first weavestructure includes one or more portions with a looser weave structurethan the second weave structure. In addition, the first weave structuremay adjoin the bag portion. Furthermore, the first weave structure mayhave a 2/2 structure. In this case, the 2/2 structure may be constitutedof 3 to 5 warp yarns, or 3 to 5 weft yarns. Moreover, the second weavestructure may have a 1/1 structure. In this case, the 1/1 structure maybe constituted of 2 to 5 warp yarns or 2 to 5 weft yarns. In addition,the interlace densities of the first weave structure and the secondweave structure of the bag portion may satisfy one or more of theconditions as shown in (1) to (3) below. (However, this excludes a casewhere the interlace density of the first weave structure and theinterlace density of the second weave structure are both 4/3).

-   -   (1) The interlace density of the bag portion is 1/2 or less.    -   (2) The interlace density of the first weave structure is from        2/3 or more to 4/3 or less.    -   (3) The interlace density of the second weave structure is 4/3        or more. Furthermore, the hollow-weave airbag according to the        first aspect of the invention may possess a third weave        structure that adjoins a side opposite the bag portion side of        the second weave structure. In this case, the third weave        structure may have a looser weave structure than the second        weave structure. Moreover, the value for the interlace density        of the first weave structure may be a value between the value        for the interlace density of the second weave structure and the        value for an interlace density of the third weave structure. In        addition, the third weave structure may have an n/m structure        (where n and m are both integers of 1 or more, excluding,        however, a 1/1 structure). Moreover, the interlace density of        the third weave structure may be 1 or less.

Furthermore, a hollow-weave airbag according to a second aspect of theinvention is constituted of a bag portion and a closed portion thatadjoins the bag portion and has two or more weave structures. Of weavestructures that constitute the closed portion, a weave structure thatadjoins the upper bag portion is a reversed bag structure where a lowercloth thereof is formed of warp yarns and weft yarns that constitute anupper cloth of the bag portion, and an upper cloth thereof is formed ofwarp yarns and weft yarns that constitute a lower cloth of the bagportion. Moreover, the reversed bag structure may be formed of warpyarns and 3 to 7 and weft yarns that constitute the weave structure ofthe bag portion.

Furthermore, at least one portion of an outer surface of the bag portionand/or the closed portion of both the hollow-weave airbags according tothe first and second aspects may be coated. Moreover, the weavestructure that constitutes the boundary of the bag portion and theclosed portion of both the hollow-weave airbags according to the firstand second aspects may have a curved line structure.

The hollow-weave airbag according to the first aspect lessens suddenvariations in yarn density at the boundary of the bag portion and theclosed portion, and because the weave structure that adjoins the closedportion has a similar roughness, stress is not concentrated ondeployment and opening of stitches can be suppressed. Furthermore, inthe hollow-weave airbag according to the second aspect, the boundary ofthe bag portion and the closed portion becomes a buffer portion for airpressure and can suppress the opening of stitches because the weavestructure of the closed portion that adjoins the bag portion has thereversed bag structure. Therefore, the hollow-weave airbags according tothe first and second aspects secure sufficient airtightness at theboundary of the bag portion and the closed portion even on deployment,and can maintain the deployed state for the certain time or more. Inaddition, the hollow-weave airbags according to the first and secondaspects can suppress the opening of stitches even when the boundary ofthe bag portion and the closed portion has a curved line structure andsecure excellent airtightness. Furthermore, the design of thehollow-weave airbag has a high degree of freedom and high versatility.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially enlarged cross-sectional view of a hollow-weaveairbag according to a first embodiment of the invention;

FIG. 2 is a partially enlarged cross-sectional view of a hollow-weaveairbag according to a second embodiment of the invention;

FIG. 3 is an explanatory drawing of a minimum component unit of a weavestructure of the hollow-weave airbag according to the first embodimentof the invention;

FIG. 4 is an explanatory drawing of a minimum component unit of a weavestructure of the hollow-weave airbag according to the second embodimentof the invention;

FIG. 5 is an explanatory drawing of a minimum component unit of a weavestructure of a hollow-weave airbag according to a third embodiment ofthe invention;

FIG. 6 is an explanatory drawing of a minimum component unit of a weavestructure of a hollow-weave airbag according to a fourth embodiment ofthe invention;

FIG. 7 is an explanatory drawing of a minimum component unit of a weavestructure of a hollow-weave airbag according to comparison example 1;

FIG. 8 is an explanatory drawing of a minimum component unit of a weavestructure of a hollow-weave airbag according to comparison example 2;

FIG. 9 is a graph of changes over time for the internal pressure of eachhollow-weave airbag according to the embodiments and comparisonexamples; and

FIG. 10A is an explanatory drawing of the interlace density of a 1/1plain weave, FIG. 10B is an explanatory drawing of the interlace densityof a 2/2 basket weave structure, FIG. 10C is an explanatory drawing ofthe interlace density of a 2/1 twill weave, and FIG. 10D is anexplanatory drawing of the interlace density in a bag portion plainweave.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, embodiments of the invention are described in detail withreference to the drawings.

FIG. 1 shows a partially enlarged cross-sectional view of a hollow-weaveairbag according to a first embodiment of the invention. Furthermore,FIG. 3 shows an explanatory drawing of a minimum component unit of aweave structure. The overall form of the hollow-weave airbag 1Aaccording to the invention has no specific limitations, but normally, itis formed with a substantially rectangular shape. In addition, thehollow-weave airbag 1A according to this embodiment has a bag portion 11that deploys by means of an inflow of gas from an opening portion (notshown on drawing) that is provided in an arbitrary location on thehollow-weave airbag 1A, and a closed portion 12 that adjoins the bagportion 11 and is closed such that a gas leak will not occur.Furthermore, the closed portion 12 is constituted of a first weavestructure 12A, a second weave structure 12B and a third weave structure12C, adjoining each other in sequence from the bag portion side. Theclosed portion 12 is formed of a single-layered weave, but the inventionis not specifically limited to this. Moreover, the hollow-weave airbagaccording to this embodiment is provided with a curved-line shape closedportion even on a central portion, by means of which the hollow-weaveairbag according to this embodiment is divided into a plurality ofexpansion chambers, but the invention is not specifically limited tothis.

The closed portion of the hollow-weave airbag according to thisembodiment possesses two or more structures and is constituted of, insequence from the bag portion side, the first weave structure and thesecond weave structure, which adjoins a side of the first weavestructure opposite the bag portion side (the opposite side to the bagportion side). Furthermore, the first weave structure includes one ormore portions with a looser weave structure than the second weavestructure. FIGS. 1 and 3 are diagrams where the first weave structure12A is looser than the second weave structure 12B. Here, thedescription, “the first weave structure is looser than the second weavestructure,” indicates a case where at least one of the conditions (1)and (2) below are satisfied.

-   -   (1) When the first weave structure has an “n1 (m1 weave        structure” and the second weave structure has an “n2 (m2 weave        structure,” n1, m1, n2 and m2 are all integers of 1 or more and        (n1+m1)>(n2+m2)    -   (2) (The interlace density of the first weave structure)<(The        interlace density of the second weave structure).

The aforementioned interlace density is a value calculated according tothe formula below. In general, when the weave structure is an α−β basketweave structure, the interlace density has the relationship, (α+β)/αβ.Interlace density=a/b

-   -   a: Number of interlacing points on a complete structure chart        (minimum component unit that shows weave structure). (Number of        points where warp yarns and weft yarns intersect. On FIGS. 10A        to 10D, a white circle indicates an interlacing point. The        number of interlacing points is the number of these white        circles. The number of interlacing points on FIG. 10A is 8, FIG.        10B is 16, FIG. 10C is 12, and FIG. D is 8.)    -   b: Number of meshes on the complete structure chart (number of        grids. FIG. 10A has 4, FIG. 10B has 16, FIG. 10C has 9, and FIG.        10D has 16).

The form of the first weave structure and the second weave structure arenot specifically limited provided that the above conditions aresatisfied. For example, an appropriate publicly known weave, such as aplain weave, a twill weave, a basket weave or a diagonal weave, may beselected as the first weave structure and the second weave structure.Furthermore, a structure such as an n/n′ structure (where n and n′ areintegers of 1 or more, and n may be equal to n′), such as a 1/1structure, a 2/1 structure, a 1/2 structure, a 2/2 structure, a 2/3structure, a 3/3 structure, a 3/2 structure, or the like may be selectedand combined as the weave structure for the first weave structure andthe second weave structure. Furthermore, it is preferable that theinterlace density of the first weave structure be from 2/3 or more to4/3 or less, but it is more preferable that it be larger than 2/3 andless than 4/3, and it is even more preferable that it be from 5/6 ormore to 1 or less. Moreover, it is preferable that the interlace densityof the second weave structure be 4/3 or more, but it is more preferablethat it be larger than 4/3, and it is even more preferable that it be3/2 or more. However, the interlace densities for the first weavestructure and the second weave structure may not both be 4/3.

More specifically, a 3/3 basket weave structure (interlace density=2/3),a 3/2 basket weave structure (interlace density=5/6), a 2/2 basket weavestructure (interlace density=1, see FIG. 10B), a 2/2 twill weavestructure (interlace density=1), a 2/1 twill weave structure (interlacedensity=4/3, see FIG. 10C), or the like can be proposed as the firstweave structure. Furthermore, a 2/1 twill weave structure (interlacedensity=4/3), a 1/2 basket weave structure (interlace density=3/2), a1/1 plain weave structure (interlace density=2), or the like can beproposed as the second weave structure. Even more specifically, forexample, the first weave structure 12A may be given a 2/2 weavestructure (preferably a 2/2 basket weave structure) and the second weavestructure 12B may be given a 1/1 plain weave structure, as shown in FIG.3. Employing this kind of configuration is preferable since it enablesairtightness to be further improved.

Furthermore, there are no specific limitations regarding the number ofweft yarns and warp yarns that constitute the first weave structure andthe second weave structure, and various numbers are possible dependingon requirements. In the example of the weave structure in theaforementioned closed portion given above, i.e. when utilizing the 2/2structure (preferably a 2/2 basket weave structure) as the first weavestructure, it is preferable that the number of weft yarns and warp yarnsthat constitute the 2/2 structure be from 3 to 5, but it is morepreferable that it be from 3 to 4, or 4 to 5. Furthermore, also in theexample of the weave structure in the closed portion given above, i.e.when utilizing the 1/1 plain weave structure as the second weavestructure, it is preferable that the number of weft yarns and warp yarnsthat constitute the 1/1 plain weave structure be from 2 to 5, but it ismore preferable that it be from 3 to 5, and it is even more preferablethat it be from 4 to 5. Each of these configurations is preferable sincethey enable a hollow-weave airbag to be produced that has an even moreexcellent airtightness. Moreover, when the first weave structure has the2/2 structure (preferably the 2/2 basket weave structure) and the secondweave structure has the 1/1 plain weave structure, it is preferable toset the number of weft yarns and warp yarns that constitute the 2/2structure and the 1/1 structure within the ranges detailed above, sincethis will enable airtightness to be further improved.

In addition, in the above description of the hollow-weave airbagaccording to the invention, “constituted of, in sequence from the bagportion side, the first weave structure and the second weave structure,which adjoins a side of the first weave structure opposite the bagportion side, and the first weave structure includes a portion with alooser weave structure than the second weave structure,” if this portionis included in the closed portion, then it may be included anywhere inthe closed portion. Normally, the first weave structure adjoins the bagportion. In other words, as shown in FIGS. 1 and 3, the first weaveportion 12A adjoins the opposite bag portion side of the bag portion 11and, therefore, the portion indicated in the aforementioned description,“constituted of, in sequence from the bag portion side, of the firstweave structure and the second weave structure, which adjoins a side ofthe first weave structure opposite the bag portion, and the first weavestructure includes a portion with a looser weave structure than thesecond weave structure,” (the first weave structure 12A and the secondweave structure 12B in FIGS. 1 and 3) in turn exist adjoining the bagportion 11.

Furthermore, no specific limitation is made regarding the number ofportions in the closed portion indicated in the aforementioneddescription, “constituted of, in sequence from the bag portion side, ofthe first weave structure and the second weave structure, which adjoinsa side of the first weave structure opposite the bag portion, and thefirst weave structure includes a portion with a looser weave structurethan the second weave structure,” provided that there is at least one.The number of the aforementioned portions in the hollow-weave airbagaccording to the invention is usually 1 to 4, but it is more preferablethat the number be 1 to 3, and it is even more preferable that thenumber be 1, as shown in FIGS. 1 and 3.

As shown in FIG. 1, the hollow-weave airbag according to the inventionmay have, as a structure that constitutes the closed portion 12, thethird weave structure adjoining a side of the second weave structure 12Bopposite the bag portion side. By having the third weave structure, thevariation in the interlace densities in the bag portion and the closedportion are further lessened, which disperses stress caused by airpressure on deployment, and is preferable since it enables an excellentairtightness to be achieved. There are no specific limitations regardingthe form of the third weave structure, and it may be given various weavestructures as necessary. For example, an appropriate publicly knownweave, such as a plain weave, a twill weave, a basket weave or adiagonal weave, may be selected for the third weave structure. The thirdweave structure is normally formed of a single-layered weave structure,but it is not specifically limited to this. Moreover, the third weavestructure may be given an n/m structure (where n and m are integers of 1or more, and n may be equal to m. However, the 1/1 structure isexcluded) such as the 2/1 structure, the 1/2 structure, the 2/2structure, the 2/3 structure, the 3/3 structure, the 3/2 structure, orthe like. It is more preferable to be able to use a n′/m′ basket weavestructure (where n′ and m′ are integers of 3 or more, and n′ may beequal to m′) such as the 3/3 basket weave structure, a 3/4 basket weavestructure, a 4/4 basket weave structure, a 5/5 basket weave structure,or the like.

More specifically, of these options, it is preferable that the thirdweave structure be looser than the second weave structure. Here, “looserweave structure” has the same meaning as the definition detailed above.(However, in the above definition, “the first weave structure” should bereplaced by “the third weave structure.”) Furthermore, there are nospecific limitations regarding the interlace density of the weavestructure 3, but from the point of view of airtightness, it ispreferable that the interlace density of the first weave structure be avalue between the interlace density of the second weave structure andthe interlace density of the third weave structure. More specifically,the interlace density of the third weave structure should be one orless, preferably less than 1, more preferably 5/6 or less and even morepreferably 2/3 or less. For example, the 2/2 basket weave structure(interlace density=1), the 3/2 basket weave structure (interlacedensity=5/6), the 3/3 basket weave structure (interlace density=2/3),the 4/4 basket weave structure (interlace density=1/2), a 5/5 basketweave structure (interlace density=2/5), or the like can be proposed asweave structures that fall into these ranges.

The configuration of the closed portion of the hollow-weave airbagaccording to this invention is not specifically limited provided thatthese conditions are satisfied, and various configurations are possibleas required. It is preferable that the configuration of the closedportion be as follows. The interlace density of the first weavestructure should be from 2/3 or more to 4/3 or less, but it ispreferable that it be larger than 2/3 and less than 4/3, and it is morepreferable that it be from 5/6 or more to 1 or less. The interlacedensity of the second weave structure should be 4/3 or more, but it ismore preferable that it be larger than 4/3, and it is even morepreferable that it be 3/2 or more. (However, the interlace densities forthe first weave structure and the second weave structure may not both be4/3). The interlace density of the third weave structure should be 1 orless, but it is more preferable that it be less than 1, and it is evenmore preferable that it be 5/6 or less. More specifically, an interlacedensity that falls within the aforementioned ranges may be a suitablecombination configuration of the weave structures shown above. Apreferable configuration is, as shown in FIG. 3, a configuration wherethe first weave structure 12A has the 2/2 structure (the 2/2 basketweave structure, the 2/2 twill weave structure, or the like), the secondweave structure 12B has the 1/1 structure (1/1 plain weave structure orthe like), and the third weave structure 12C has a n/m structure (wheren and m are integers of 3 or more, and n may be equal to m).

There are no specific limitations regarding the form of the bag portion11 of the hollow-weave airbag according to this invention, and variousforms are possible as required. Normally, the bag portion is formed froma double-layered weave. Furthermore, an appropriate publicly knownweave, such as a plain weave, a twill weave, a basket weave or adiagonal weave, may be selected as the weave of the bag portion 11.Moreover, there are also no specific limitations regarding the weavestructure of the bag portion. For example, an n/n′ bag structure (wheren and n′ are integers of 1 or more, and n may be equal to n′), such as a1/1 bag structure, a 2/1 bag structure, a 1/2 bag structure, a 2/2 bagstructure, a 2/3 bag structure, a 3/3 bag structure, a 3/2 bagstructure, or the like may be proposed as the weave structure for thebag portion. Furthermore, the interlace density for the bag portion isnormally 1/2 or less, but it is preferable that it be 2/5 or less. Here,it is preferable that the weave structure of the bag portion have asmaller interlace density than, of the structures that constitute theclosed portion, the structure that adjoins the opposite bag portion sideof the bag portion. A more specific example of the weave structure ofthe bag portion is proposed in the bag portion plain weave (interlacedensity 1/2) as shown in FIG. 10D. (the “empty” spaces shown in FIG. 10Dare portions with no yarn, “−” indicates a weft yarn, “|” indicates awarp yarn, and “+” indicates an apex where a warp yarn and a weft yarncross.)

As a specific example for a configuration of the bag portion and theclosed portion of the hollow-weave airbag according to the invention, anitem can be proposed where the interlace densities of the bag portion,the first weave structure and the second weave structure should satisfyat least one of the conditions (1) to (3) detailed below, but it ispreferable that at least two be satisfied, and it is more preferablethat all three of them be satisfied. (However, this excludes a casewhere the interlace density of the first weave structure and theinterlace density of the second weave structure are both 4/3).Furthermore, when the closed portion possesses the third weavestructure, as a specific example for a configuration of the bag portionand the closed portion of the hollow-weave airbag according to theinvention, an item can be proposed where at least one of the conditions(1) to (4) detailed below is satisfied, but it is preferable that atleast two be satisfied, and it is more preferable that at least three besatisfied, and it is even more preferable that all four of them besatisfied. (However, this excludes a case where the interlace density ofthe first weave structure and the interlace density of the second weavestructure are both 4/3).

-   -   (1) The interlace density of the bag portion is 1/2 or less.    -   (2) The interlace density of the first weave structure is from        2/3 or more to 4/3 or less.    -   (3) The interlace density of the second weave structure is 4/3        or more.    -   (4) The interlace density of the third weave structure is 1 or        less.

Normally in conventional hollow-weave airbags, the interlace densitiesof the bag portion and the closed portion are different and there arelarge variations in the interlace density at a boundary portion of thebag portion and the closed portion. Therefore, on deployment, stressconcentrates at the boundary portion of the bag portion and the closedportion where the interlace density varies, causing a susceptibility togas leaks due to opening of stitches. Furthermore, the opening ofstitches above a predetermined level may cause fracturing to a coatinglayer. On the other hand, the hollow-weave airbag according to theinvention employs the configuration as detailed above and, byalleviating the variations in interlace density at the bag portion andthe closed portion, disperses the stress caused by air pressure ondeployment. As a result of suppressing the opening of stitches,excellent airtightness is achieved on deployment and the deployed statecan be maintained for a predetermined period of time.

FIG. 2 shows a partially enlarged cross-sectional view of a hollow-weaveairbag according to a second embodiment of the invention. Furthermore,FIG. 5 shows an explanatory drawing of a minimum component unit of aweave structure. In the same way as for the first embodiment of thehollow-weave airbag, the overall form of the hollow-weave airbag 1Baccording to the second embodiment of the invention has no specificlimitations, but normally, it is formed with a substantially rectangularshape. Thus, the hollow-weave airbag 1B according to the secondembodiment has a bag portion 11 that deploys by means of an inflow ofgas from an opening portion (not shown on drawing) that is provided inany location on the hollow-weave airbag 1B, and a closed portion 12 thatadjoins the bag portion 11 and is closed such that a gas leak will notoccur. The closed portion 12 is constituted of a reversed bag structure121 that adjoins the opposite bag portion side of the bag portion 11,and a third weave structure 12C that adjoins a side of the reversed bagstructure 121 opposite the bag portion side.

Of the weave structures that constitute the closed portion 12 of thehollow-weave airbag 1B according to the second embodiment, the weavestructure that adjoins the bag portion 11 is, as shown in FIG. 2, thereversed bag structure 121. In other words, a lower cloth 121B of thereversed bag structure 121 is formed of warp yarns and weft yarns thatconstitute an upper cloth 111 of the bag portion 11, and an upper cloth121A of the reversed bag structure 121 is formed of warp yarns and weftyarns that constitute a lower cloth 112 of the bag portion 11. Employingthis configuration lessens stress caused by gas pressure and suppressesopening of stitches of a boundary portion and can prevent gas leaks, asa result of the boundary portion being used as a buffer to the gaspressure.

Provided that the reversed bag structure 121 is formed such that thelower cloth 121B of the reversed bag structure 121 is formed of warpyarns and weft yarns that constitute the upper cloth 111 of the bagportion 11, and the upper cloth 121A of the reversed bag structure 121is formed of warp yarns and weft yarns that constitute the lower cloth112 of the bag portion 11, there are no specific limitations on theweave structure thereof. It is preferable, however, that in ahollow-weave airbag according to the second embodiment, the reversed bagstructure 121 be formed of the 3 to 7 weft yarns that constitute theweave structure of the bag portion 11, and it is more preferable that itbe formed of 3 to 6 weft yarns, and it is even more preferable that itbe formed of 3 to 5 weft yarns. This configuration is preferable becauseit further suppresses opening of stitches at the boundary of the bagportion and the closed portion and can secure an even more excellentairtightness.

Furthermore, as shown in FIG. 2, in the hollow-weave airbag according tothe second embodiment of the invention, the third weave structure 12Cmay be provided on the side of the reversed bag structure 121 oppositethe bag portion side. At least one third of the weave structure 12C mayadjoin the side of the reversed bag structure 121 opposite the bagportion side, but there are no specific limitations regarding the numberthereof and it may be constituted of one type of structure, or of astructure with two or more different weave structures.

There are no specific limitations regarding the form of the bag portion11 and the third weave structure 12C of the hollow-weave airbagaccording to the second embodiment. Normally, the bag portion 11 isformed from a double-layered weave and the third weave structure isformed from a single-layered weave. Furthermore, an appropriate publiclyknown weave, such as a plain weave, a twill weave, a diagonal weave, orthe like may be selected as the weave of the bag portion 11 and thethird weave structure 12C. Moreover, there are also no specificlimitations regarding the weave structures of the bag portion 11 and thethird weave structure 12C, and for example, an n/n′ structure (where nand n′ are integers of 1 or more, and n may be equal to n′), such as a1/1 structure, a 2/1 structure, a 1/3 structure, a 2/2 structure, a 3/3structure, or the like may be used. It is preferable that, as shown inFIG. 5, the weave structure of the bag portion 11 be the 1/1 bagstructure. Furthermore, of the structures that constitute the closedportion 12, the third weave structure 12C should be an n/n′ structure(where n and n′ are integers of 1 or more, and n may be equal to n′,excluding n and n′=1) with a lower interlace density than the 1/1structure, such as the 2/2 or the 3/3 structure.

In the hollow-weave airbags according to the first and secondembodiments, at least one portion of an outer surface of the bag portionand/or the closed portion may be coated with silicone resin or the like.Doing this enables a further increase in airtightness. In this case,there are no specific limitations regarding the coating locations if atleast one portion of the outer surface of the bag portion and/or theclosed portion is coated, but it is preferable that a location be theouter surface of the bag portion and/or the closed portion that includesat least the boundary of the bag portion and the closed portion.

The weave structure that constitutes the boundary of the bag portion andthe closed portion of the hollow-weave airbags according to the firstand second embodiments may have a straight-line structure, but acurved-line weave structure is also possible. Using the curved-linestructure is preferable because it increases freedom of design of thehollow-weave airbag, enables the gas pressure to be suitably dispersedand possesses the same excellent air tightness as the straight-linestructure.

EXAMPLES

Hereafter, the embodiments of the invention will be explained in moredetail by citing practical examples.

(1) Configuration of Hollow-Weave Airbag

The hollow-weave airbags according to the practical examples andcomparison examples are woven using 350 dtex 108 nylon material yarn forthe warp yarns and weft yarns, and carried out with the number ofimplanted yarns at 135/inch longitudinally and 122/inch laterally (1/2of that figure in one bag portion), such that the boundary of the bagportion 11 and the closed portion 12 form a curved-line structure.Furthermore, coating is carried out in the hollow-weave airbagsaccording to the practical examples and comparison examples, so that thecoating amount of the upper cloth (front side) and the lower cloth (rearside) are both 60 g/m2. FIGS. 3 to 8 show minimum component units ofweave structures of the hollow-weave airbag according to the practicalexamples and comparison examples. FIG. 3 shows the minimum componentunit of practical example 1 of the hollow-weave airbag, FIG. 4 showspractical example 2, FIG. 5 shows practical example 3, FIG. 6 showspractical example 4, FIG. 7 shows comparison example 1, and FIG. 8 showscomparison example 2. The weave structure for all the practical examplesand comparison examples of the hollow-weave airbag is the 1/1 bagstructure.

Practical examples 1 and 2 are practical examples of the firstembodiment of the hollow-weave airbag. In practical example 1, of theweave structures that constitute the closed portion 12, the first weavestructure 12A that adjoins the bag portion 11 is formed by a 2/2 basketweave structure constituting of 4 weft yarns, and the second weavestructure 12B that adjoins the side of the first weave structure 12Aopposite the bag portion side is formed by a 1/1 plain structureconstituting of 2 weft yarns. Furthermore, in practical example 2, ofthe weave structures that constitute the closed portion 12, the firstweave structure 12A that adjoins the bag portion 11 is formed by a 2/2basket weave structure constituting of 4 weft yarns, and the secondweave structure 12B that adjoins the side of the first weave structure12A opposite the bag portion side is formed by a 1/1 plain structureconstituting of 4 weft yarns. Moreover, both practical examples 1 and 2have a 3/3 structure third weave structure 12C on the side of the secondweave structure 12B opposite the bag portion side.

In addition, practical examples 3 and 4 are practical examples of thesecond embodiment of the hollow-weave airbag. In practical example 3, ofthe weave structures that constitute the closed portion 12, the weavestructure that adjoins the bag portion 11 is the reversed bag structure121 that is constituted of warp yarns and 3 weft yarns, in practicalexample 4, of the weave structures that constitute the closed portion12, the weave structure that adjoins the bag portion 11 is the reversedbag structure 121 that is constituted of warp yarns and 6 weft yarns.Note that in the closed portion 12, the third weave structure 12C thatadjoins the side of the reversed bag structure 121 opposite the bagportion side has a single-layered structure (3/3 structure).

On the other hand, in comparison example 1, of the weave structures thatconstitute the closed portion 12, the weave structure that adjoins thebag portion 11 has a straight-line structure that is constituted of oneclosed portion weave structure, and the structure adjoining this is asingle-layered structure (3/3 structure). Furthermore, in comparisonexample 2, of the weave structures that constitute the closed portion12, the weave structure that adjoins the bag portion 11 is a 1/1 plainweave structure, and the structure adjoining the 1/1 plain weavestructure is a single-layered structure (3/3 structure).

(2) Evaluation of Performance

The changes over time for the internal pressure of each hollow-weaveairbag according to the practical examples and comparison examples wasinvestigated using a method whereby an inflator was attached to eachhollow-weave airbag according to the practical examples and comparisonexamples to cause deployment. Table 1 below shows the results.Furthermore, FIG. 9 shows a graph of changes over time for the internalpressure of each hollow-weave airbag according to the practical examplesand comparison examples. Note that the measurement results in Table 1are, regarding each hollow-weave airbag according to the practicalexamples and comparison examples, mean values measured with a samplenumber of N=2. Airtightness was evaluated based on these results.

TABLE 1 Airbag internal pressure (kPa) Time Practical PracticalPractical Practical Comparison Comparison (ms) example 1 example 2example 3 example 4 example 1 example 2   0 98 99 98 97 96 100   60 9293 91 88 92 93  80 90 92 90 86 89 89  100 87 90 86 83 85 86  300 74 7674 70 68 71 1000 59 61 58 55 43 53 3000 42 42 42 37 16 30 6000 29 28 3122  4 14

(3) Effect of the Examples

Looking at Table 1 and FIG. 9, for each of the hollow-weave airbagsaccording to comparison examples 1 and 2, the internal pressure of theairbags 6 seconds after deployment was 4 kPa and 14 kPa. Compared withthis, for practical examples 1 and 2, which are hollow-weave airbagsaccording to the first embodiment, the internal pressure of the airbags6 seconds after deployment was 29 kPa and 28 kPa, and for practicalexamples 3 and 4, which are hollow-weave airbags according to the secondembodiment, the internal pressure of the airbags 6 seconds afterdeployment was 31 kPa and 22 kPa. Based on the results, it wasunderstood that all of the practical examples 1 to 4 possessed a moreexcellent airtightness than the hollow-weave airbags of the comparisonexamples. More specifically, it was understood that the hollow-weaveairbags of practical examples 1 and 2 and the hollow-weave airbag of thepractical example 3 that was formed with a reversed bag structure using3 weft yarns possess a more excellent airtightness because the internalpressure of each of the hollow-weave airbags 6 seconds after deploymentwas large.

Note that the invention is not limited to the aforementioned specificpractical examples, and various modifications are possible depending onpurpose and application.

1. A hollow-weave airbag comprising: a bag portion; and a closed portion that has two or more weave structures and adjoins the bag portion; and wherein the closed portion includes, in sequence from a bag portion side, a first weave structure and a second weave structure, which adjoins a side of the first weave structure opposite the bag portion side, and the first weave structure includes one or more portions with a looser weave structure than the second weave structure; wherein the closed portion is formed of a single layered weave; wherein an interface density of the second weave structure is 4/3 or more; and wherein at least one portion of an outer surface of the bag portion and the closed portion, which includes at least a boundary of the bag portion and of the closed portion, is coated.
 2. The hollow-weave airbag according to claim 1, wherein the first weave structure adjoins the bag portion.
 3. The hollow-weave airbag according to claim 1, wherein the first weave structure is a 2/2 structure.
 4. The hollow-weave airbag according to claim 3, wherein the 2/2 structure is constituted of 3 to 5 warp yarns and 3 to 5 weft yams.
 5. The hollow-weave airbag according to claim 1, wherein the second weave structure has a 1/1 structure.
 6. The hollow-weave airbag according to claim 5, wherein the 1/1 structure is constituted of 2 to 5 warp yarns and 2 to 5 weft yams.
 7. The hollow-weave airbag according to claim 1, wherein an interlace density of the bag portion, the first weave structure and the second weave structure satisfies at least one of the conditions shown in (1) to (3) below, excluding, however, a case where the interlace density of the first weave structure and the interlace density of the second weave structure are both 4/3, (1) the interlace density of the bag portion is 1/2 or less, (2) the interlace density of the first weave structure is from 2/3 or more to 4/3 or less, and (3) the interlace density of the second weave structure is 4/3 or more.
 8. The hollow-weave airbag according to claim 1, wherein a third weave structure adjoins a side of the second weave structure opposite the bag portion side.
 9. The hollow-weave airbag according to claim 8, wherein the third weave structure has a looser weave structure than the second weave structure.
 10. The hollow-weave airbag according to claim 8, wherein the value of the interlace density of the first weave structure is a value between the value for the interlace density of the second weave structure and the value for an interlace density of the third weave structure.
 11. The hollow-weave airbag according to claim 8, wherein the third weave structure has an n/m structure (where n and m are both integers of 1 or more, excluding, however, a 1/1 structure).
 12. The hollow-weave airbag according to claim 8, wherein the interlace density of the third weave structure is 1 or less.
 13. A hollow-weave airbag that includes a bag portion and a closed portion that has 2 or more weave structures and adjoins the bag portion, wherein: at least one of the weave structures that constitute the closed portion, and that adjoins the bag portion, has a reversed bag structure; the reversed bag structure having a lower cloth and an upper cloth, where the lower cloth of the reversed bag structure is formed of warp yarns and weft yarns that constitute an upper cloth of the bag portion, and the upper cloth of the reversed bag structure is formed of warp yarns and weft yarns that constitutes a lower cloth of the bag portion.
 14. The hollow-weave airbag according to claim 13, wherein the reversed bag structure is formed of warp yarns and 3 to 7 and weft yarns that constitute the weave structure of the bag portion.
 15. The hollow-weave airbag according to claim 1, wherein at least one portion of an outer surface of the bag portion and/or the closed portion is coated.
 16. The hollow-weave airbag according to claim 1, wherein the weave structure that constitutes the boundary of the bag portion and the closed portion has a curved line structure.
 17. The hollow-weave airbag according to claim 13, wherein at least one portion of an outer surface of the bag portion and/or the closed portion is coated.
 18. The hollow-weave airbag according to claim 13, wherein the weave structure that constitutes the boundary of the bag portion and the closed portion has a curved line structure. 